In this dissertation I present my research on the effective interactions of colloidal particles induced by a smaller species, as well as the structure of colloidal particles undergoing freeze casting. In this research I have used a wide variety of computational techniques in order to understand these systems. Specifically, in Chapter 2 I study nanoparticle haloing in a system of silica microspheres and highly charged polystyrene nanoparticles. Computer simulations are employed to determine the effective microsphere0́3 microsphere potential induced by the nanoparticles. From these simulations I am also able to determine the degree of nanoparticle adsorption on the microsphere surface. In Chapter 3 I investigate the depletion interaction in a system of charged microspheres and rigid rods. The effect of both rod concentration and screening length is explored. In Chapter 4 I study the effective interactions between charged colloids in the presence of multivalent counterions. The role of colloid charge is investigated and the onset of like-charged attraction is determined and compared with theoretical predictions. In order to study this system, I extended the geometric cluster algorithm to efficiently simulate systems interacting through the Coulomb potential. In Chapter 5 computer simulations are employed to elucidate the experimentally observed crystal phases of the Q and MS-2 virus particles in solution with multivalent salt and non-adsorbing polymer. Freeze casting is studied in Chapter 6. In this process colloidal particles are pushed by an advancing ice front. I use molecular dynamics simulations to study the dynamics of the colloidal particles and the resulting structures formed. iii

The first five articles in this issue emphasize equilibrium phases and structures. The hard sphere properties of sterically stabilized particle suspensions are examined in the article by van Megan, Pusey and Bartlett, a colloidal compound is discussed by Hachisu and attractive interactions are shown to produce a full complement of phase transitions including a liquid/gas transition by Emmett and Vincent. Recent theoretical interest in the nature of melting in two dimensions has led to the investigation of the melting transition in colloidal systems where the particles are constrained to a single layer. Murray, Van Winkle and Wenk present experimental results supporting the view that two dimensional melting is mediated by two second order transitions, while Tang, Armstrong, Mockler and O'Sullivan present results suggesting a first order process in a similar colloidal monolayer.

Recently, there has been a surge of activity to elucidate the behavior of highly charged soft matter and Coulomb fluids in general. Such systems are ubiquitous, especially in biological matter where the length scale and the strength of the interaction between highly charged biomolecules are governed by strong electrostatic effects. Several interesting limits have been discovered in the parameter space of highly charged many-particle Coulomb matter where analytical progress is possible and completely novel and unexpected results have been obtained. One of the challenges in highly charged matter is to correctly describe systems with finite coupling strength in the transition regime between weak and strong couplings. After studying the fluctuations of both, several theories have been developed that describe this experimentally highly relevant regime. At the same time, computer simulation algorithms and computing power have advanced to the level where all-ion simulations, including many-body and polarization effects, are possible; the new theories thus can be subjected to numerical confirmation. Another important question is the effect of the structural disorder on electrostatic interactions. It has recently been demonstrated, both theoretically and experimentally, that charge disorder can impose long-range interaction between charged or even uncharged surfaces. These interactions might become very significant in biological processes. Filling a void in the literature, this volume cross-pollinates different theoretical and simulation approaches with new experiments and ties together the low temperature, high coupling constant, and disorder parameters in a unified description of the electrostatic interactions, which largely determine the stability and conformations of most important biological macromolecules. With striking graphical illustrations, the book presents a unified view of the current advances in the field of Coulomb (bio)colloidal systems, building on previous literature that summarized the field over 20 years ago. Leading scientists in the field offer a detailed introduction to different modern methods in statistical physics of Coulomb systems. They detail various approaches to elucidate the behavior of strongly charged soft matter. They also provide experimental and theoretical descriptions of disorder effects in Coulomb systems, which have not been discussed in any other book.